The present invention relates to the field of electrochemical processing, and more particularly to an apparatus and method for uniformly polishing the interior of pipes which include both uniform portions and nonuniform portions. The predominant current usage of the present inventive improved pipe electropolishing apparatus and method is in the in place polishing of the inner surfaces of pipes.
It is known in the art to deposit and/or remove materials by passing an electric current through a fluid electrolyte which is in contact with a conductive electrode. Materials are exchanged between the electrolyte and the electrode depending upon the direction of current flow and the ionization of materials to be deposited on or removed from the electrode. Electroplating is a well known application of this general method. Electropolishing is also well known in the art. In the electropolishing process, irregularities and deposits on a surface are removed by causing such to be drawn into the electrolyte solution.
An example is the in place electrochemical polishing of a pipe. In such an example, a cathode is drawn through the pipe while an electrolyte solution is simultaneously piped through the pipe. The pipe acts as an anode and is electrochemically polished in the process. Since the electrolyte solution must be continuously pumped through the pipe during the process, it is most practical to recirculate the solution.
A piping system will generally consist of uniform (e.g., straight, no welds or joints, etc.) sections of pipe and of nonuniform (e.g., bent, welded joint fittings, etc.) sections joining such uniform sections. For various reasons, it happens that the nonuniform portions of pipe tend to become more pitted and uneven during manufacture and in use than do the uniform portions. An alternative in the prior art has been to over polish the uniform sections in order to make certain that the nonuniform portions are sufficiently polished on the interior. However, this alternative is wasteful of time, materials, and energy. The only other alternative has been to polish the interior of the pipes to a lesser degree, leaving the nonuniform portions less than perfectly polished. However, this alternative is much less than desirable, since leaving an uneven surface on the interior of the nonuniform portions continues to cause the same problems which necessitated the polishing in the first place.
It would be advantageous to have an electropolishing system which would adequately polish nonuniform pipe segments without over polishing the uniform segments. However, to the inventor""s knowledge, no such system has existed in the prior art. All prior art systems have required either over polishing uniform sections or under polishing nonuniform sections, since there has been no provision for adjusting the amount of polishing in the different sections, as required.
Accordingly, it is an object of the present invention to provide an apparatus and method for evenly polishing all portions of the interior of a pipe system.
It is still another object of the present invention to provide an apparatus and method for polishing nonuniform portions of a pipe more than uniform sections thereof, such that the end result will be a generally evenly polished finish in all portions of the pipe.
It is yet another object of the present invention to provide an apparatus and method for varying the amount of polishing accomplished in an electropolishing system, depending upon the location of the polishing apparatus.
It is still another object of the present invention to provide an apparatus and method for adapting a pipe electropolishing apparatus such that the amount of polishing accomplished is adapted to specific portions of the pipe. It is yet another object of the present invention to provide a method and apparatus for controlling the amount of polishing accomplished in a pipe electropolishing system according to the amount of polishing required in particular sections of the pipe.
Briefly, a known embodiment of the present invention is an improved in place electropolishing apparatus for polishing a pipe. According to one described embodiment of the present invention, a cathode is drawn through a pipe at a variable rate such that the cathode can be slowed down in nonuniform sections of the pipe, wherein more polishing is required, and further such the cathode can be speeded up in uniform sections of the pipe, wherein less polishing is required. In another described embodiment of the invention, voltage to the cathode is increased while the cathode is in nonuniform portions of the pipe and decreased when the cathode is in uniform portions of the pipe.
According to one embodiment of the present invention, it is desirable to know where within a pipe the electrode is at any given time during the processing process. This can be accomplished in a number of ways, including but not limited to methods and means specifically discussed herein. For example, the cable which pulls the cathode through the pipe could be encoded, for example with colored or magnetic markings or the like, such that the position of the cathode can be generally determined by keeping track of how much cable has been pulled through. Another means would be measure the resistance and/or capacitance between the cathode and a measuring electrode placed at the end of the pipe and/or at various points along the pipe. Other means for detecting the position of the cathode could rely upon the fact that there is a significant amount of heat generated at the location of the cathode during the process. This heat could be detected by an infrared camera, by thermisters placed at specified locations along the pipe, or by marking the pipe at various locations and/or intervals with a heat sensitive crayon that changes color or melts due to heat generated by the electropolishing process.
An advantage of the present invention is that all portions of the interior of the pipe are polished sufficiently to cause such interior surface to be smooth, but not overpolished.
Another advantage of the present invention is that more polishing is accomplished in nonuniform portions of the pipe, where it is needed, than in uniform sections, wherein less polishing action is adequate.
A further advantage of the present invention is that electricity and time are not wasted in polishing uniform sections of the pipe more than is required.
Still another advantage of the present invention is that the polishing process can be speeded up, while still adequately polishing nonuniform portions of the pipe.
Yet another advantage of the present invention is that uniform portions of the pipe are not worn away by unnecessary polishing.
These and other objects and advantages of the present invention will become clear to those skilled in the art in view of the description of modes of carrying out the invention, and the industrial applicability thereof, as described herein and as illustrated in the several figures of the drawings. The objects and advantages listed are not an exhaustive list of all possible objects or advantages of the invention. Moreover, it will be possible to practice the invention even where one or more of the intended objects and/or advantages might be absent or not required in the application.
Further, those skilled in the art will recognize that various embodiments of the present invention may achieve one or more, but not necessarily all, of the above described objects and advantages. Accordingly, the listed objects and/or advantages are not essential elements of the present invention, and should not be construed as limitations.